1. Field of the Invention
This invention relates to an intermodal system for the transport of highway containers by rail.
2. Description of the Prior Art
The efficient transport of highway containers by rail has been a goal of the transportation industry for many years. In one intermodal system, containers and trailers are placed on steel rail flatcars for rail transportation. Generally, two containers or trailers are attached piggyback on the flatcars. One of the principal deficiencies of the piggyback flatcar system is the added equipment needed to load and unload the containers. In addition, the extreme weight of the flatcars greatly increases fuel costs of the system. In a desire to reduce the overall weight for fuel savings, intermodal systems that eliminate the flatcar were developed.
One such prior art system utilizes a rail bogie to support the highway container on each end. In U.S. Pat. No. 2,841,094 issued to Schumacker, the fifth wheel of the highway trailer is attached to a female coupling on the bogie. The trailer bodies are specially constructed with an inner truss to permit the rear sections of two trailers to be attached back to back between the bogies. The amount of space between the highway wheels of the trailer and the railroad tracks is limited by the height of the fifth wheel coupling mechanism attached to the bogies. The truss structure increases the tare weight of the trailer, which reduces the net cargo weight, thereby reducing revenue.
In U.S. Pat. No. 2,844,108 issued to Madden, a rail bogie includes bracket arms for gripping the axle of the highway trailer and a hydraulic jack for lifting the axle and the highway wheels off the ground. Modifications must be made to the trailer body including an additional fifth wheel, a center sill and a sub-frame to connect the bogies to the trailer. The modifications also add weight to the trailers that translates into a revenue and fuel loss.
In U.S. Pat. No. 4,416,571 issued to Krause, the trailer is modified to permit removal of the axle carrying the highway wheels before the containers are placed on the railroad bogies. A crane is needed to lower the trailers onto the railroad bogies.
Thus, there is a need for simple lightweight, cost efficient system for the transport of highway containers by rail.